During Coxsackieviral B-3 infections of Balb/c mice cytotoxic T lymphocytes are generated which lyse both viral infected and uninfected syngeneic targets. Such viral specific and "autoreactive" effector cells may play a role in the production of viral heart disease. Present studies are aimed at characterizing the physiology of both effector cell types and determining the nature of the antigen specific changes that occur in Coxsackievirus stimulated cytotoxic cells and in infected targets.